Current inducing circuit

ABSTRACT

Various example embodiments are disclosed. According to one example embodiment, a charging probe may include an alternating current (AC) input configured to receive current from an AC source, a rectifier circuit configured to rectify the current received from the AC source, a primary coil, and a control circuit configured to convert the rectified current into a regulated voltage across a primary coil. The primary coil may be configured to induce a magnetic field from the regulated voltage.

TECHNICAL FIELD

This description relates to electrical circuits.

BACKGROUND

Magnetic therapy has been found to have therapeutic effect on humans.Subjecting parts of the human body to magnetic fields may havebeneficial effects.

SUMMARY

According to one general aspect, a charging probe may include analternating current (AC) input configured to receive current from an ACsource, a rectifier circuit configured to rectify the current receivedfrom the AC source, a primary coil, and a control circuit configured toconvert the rectified current into a regulated voltage across a primarycoil. The primary coil may be configured to induce a magnetic field fromthe regulated voltage.

According to another general aspect, an apparatus may include asecondary coil configured to carry a current induced by a changingmagnetic field, a delay switch coupled to the secondary coil, and anoutput node coupled to the delay switch.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other features will beapparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing a system according to an exampleembodiment.

FIG. 2 is a circuit diagram showing a charging probe circuit and currentinducing circuit according to an example embodiment.

FIG. 3 is a circuit diagram showing a battery charging circuit accordingto an example embodiment.

FIG. 4 is a circuit diagram showing a visual indicating circuitaccording to an example embodiment.

FIG. 5 is a circuit diagram showing a tachometer circuit according to anexample embodiment.

FIG. 6A is an illustration of a magnetic therapy device according to anexample embodiment.

FIG. 6B is an illustration of a charging probe according to an exampleembodiment.

FIG. 6C is an illustration of the magnetic therapy device with thecharging probe inserted according to an example embodiment.

FIG. 6D is an illustration of a disk with a plurality of magnetsaccording to an example embodiment.

DETAILED DESCRIPTION

FIG. 1 is a circuit diagram showing a system 100 according to an exampleembodiment. According to this example, the system 100 may include acharging probe circuit 200. The charging probe circuit 200 may, forexample, receive current from an alternating current source an induce amagnetic field. The charging probe circuit 200 is described further withreference to FIG. 2.

The system 100 may also include a current inducing circuit 250. Thecurrent inducing circuit 250 may carry a current induced by a magneticfield such as the magnetic field induced by the charging probe circuit200. The current inducing circuit 250 may produce an electrical outputbased on the magnetic field. The current inducing circuit 250 isdescribed in further detail with reference to FIG. 2.

The system 100 may also include a battery charging circuit 300. Thebattery charging circuit 300 may receive a voltage source, such as theelectrical output of the current inducing circuit, and recharge arechargeable battery 102 with the voltage source. The battery chargingcircuit 300 may supply power to a motor 104. The battery chargingcircuit 300 may, for example, allow current to flow from the voltagesource to the motor 104. The battery charging circuit 300 may alsoenable the rechargeable battery 102 to supply power to the motor 104when a voltage of the voltage source drops below a threshold voltagelevel, according to an example embodiment. The battery charging circuit300 is described in further detail with reference to FIG. 3.

The system 100 may also include a visual indicating circuit 400. Thevisual indicating circuit 400 may, for example, include a plurality ofvisual indicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106h, 106 i and a microprocessor 108 which monitors a voltage level of arechargeable battery, such as the rechargeable battery 102 included inthe battery charging circuit 300. The visual indicating circuit 400 maylight a number of the plurality of visual indicators 106 a, 106 b, 106c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 i based on a monitored voltagelevel of the rechargeable battery 102, according to an exampleembodiment. The visual indicating circuit 400 is described in furtherdetail with reference to FIG. 4.

The system 100 may also include a tachometer circuit 500. The tachometercircuit 500 may include a motor 104 which controls a disk (shown in FIG.6D) upon which is mounted a plurality of magnets (also shown in FIG.6D). The tachometer circuit 500 may also include a tachometer 110 whichmonitors a magnetic field generated by the plurality of magnets andprovides a signal to a microprocessor based on the monitored magneticfield. The tachometer circuit 500 may also include a microprocessor,which may be the same microprocessor 108 used by the visual indicatingcircuit 400, which controls the motor 104 based on the signal receivedfrom the tachometer 110. The tachometer circuit 500 is described furtherwith reference to FIG. 5.

The system 100 may include one or more microprocessor inputs 112 a, 112b, and may include an input ground 112 c. The microprocessor inputs 112a, 112 b may be used to program the microprocessor 108, such as by useof a personal computer (not shown), according to an example embodiment.

FIG. 2 is a circuit diagram showing the charging probe circuit 200 andcurrent inducing circuit 250 according to an example embodiment.According to this example, the charging probe circuit 200 may include analternating current (AC) input 202. The AC input 202 may receive currentfrom an AC source (not shown), such as an electrical wall outlet (notshown). The AC input 202 may, for example, receive inputs betweenapproximately 85 to 264 volts AC between approximately 47 and 64 Hertz.This may allow the charging probe circuit 200 to receive input from manyelectrical wall outlets.

The AC input 202 may be coupled to a rectifier circuit 204. Therectifier circuit 204 may rectify the current received by the AC input202 from the AC source. The rectifier circuit 204 may include a bridgerectifier circuit. The rectifier circuit 204 may, for example, include aplurality, such as four, diodes 206 a, 206 b, 206 c, 206 d which allowcurrent to flow through the rectifier circuit 204 in only one direction,such as the direction denoted i in FIG. 2.

One of the AC input 202 nodes may be coupled to the rectifier circuit204 via a resistor 203. The resistor 203 may, for example, include aflameproof fusible resistor. The resistor 203 may protect against faultconditions. In an example embodiment,

The charging probe circuit may also include a primary coil 208 and acontrol circuit 210. The control circuit 210 may convert the rectifiedcurrent into a regulated voltage across the primary coil 208. Theprimary coil 208 may induce a magnetic field from the regulated voltage.The magnetic field may, for example, have a frequency between about tenHertz and about one hundred Hertz.

The primary coil 208 may include a first end coupled to the controlcircuit 210 and a second end coupled to the rectifier circuit 204. Theprimary coil 208 may, in an example embodiment, extend away from the ACinput 202, rectifier circuit 204, and control circuit 210. The primarycoil 208 may be enclosed in a probe, as described further with referenceto FIG. 6B.

In an example embodiment, the control circuit 210 may include a Pifilter 212. The Pi filter 212 may reduce ripple voltage across therectifier circuit 204. The Pi filter 212 may, for example, include aninductor 214, a first capacitor 216, and a second capacitor 218. Theinput capacitance may be split between the first capacitor 216 and thesecond capacitor 218 to allow the Pi filter 212 to be formed by theinductor 214. The Pi filter 212. The Pi filter 212 may, for example,filter noise associated with the AC source.

The first capacitor 216 and second capacitor 218 may have capacitancevalues of, for example, approximately 4.7 microfarads and approximately400 volts. The inductor 214 may, for example, have an inductance ofapproximately one milliHenry. The first capacitor 216 may have a firstend coupled to a first end of the rectifier circuit 204 and to a firstend of the inductor 214, and a second end coupled to a second end of therectifier circuit 204 and to a first end of the primary coil 208. Thefirst end of the inductor 214 may be coupled to the first end of thefirst capacitor 216 and to the first end of the rectifier circuit 204; asecond end of the inductor 214 may be coupled to a first end of thesecond capacitor 218. A first end of the second capacitor 218 may becoupled to the second end of the inductor 214, and a second end of thesecond capacitor 218 may be coupled to the second end of the rectifiercircuit 204 and the first end of the primary coil 208.

The control circuit 210 may also include an off-line regulator 220. Theoff-line regulator 220 may, for example, include a Power IntegrationsLK500, an integrated circuit which combines a 700 volt high voltagemetal-oxide-semiconductor field-effect transistor (MOSFET), pulse-widthmodulation controller, startup, thermal shutdown, and fault protectioncircuitry.

The off-line regulator 220 may regulate the voltage across the primarycoil 208. The off-line regulator 220 may, for example, be coupled to theprimary coil 208. In an example embodiment, the off-line regulator 220may be coupled to the second end of the inductor 214, and the rectifiercircuit 204 may be coupled to the first end of the inductor 214.

In an example embodiment, the control circuit 210 may include a thirdcapacitor 222 coupled to the primary coil 208. In this example, theoff-line regulator 220 may regulate the voltage across the primary coil208 by controlling a voltage across the third capacitor 222. Theoff-line regulator 220 may control the voltage across the thirdcapacitor 222 by controlling a current flowing into or out of theoff-line regulator 220 based on the voltage across the third capacitor222. The third capacitor 222 may, for example, have a capacitance of0.22 microfarads and approximately 50 volts.

For example, when power is applied, a high DC voltage may appear at adrain D of the off-line regulator 220. The third capacitor 222 may becharged through a switched high voltage current source connectedinternally between the drain D and a control C of the of the off-lineregulator 220. When a voltage at the control C reaches approximately 5.7volts relative to a source S of the off-line regulator 220, the internalcurrent source of the off-line regulator 220 may be turned off. Theinternal control circuitry of the off-line regulator 220 may beactivated and the high voltage internal MOSFET of the off-line regulator220 may start to switch, using the energy stored in the third capacitor222 to power the off-line regulator 220. As current ramps up in theprimary coil 208, energy may be stored in the primary coil 208. Theenergy stored in the primary coil 208 may be delivered to the currentinducing circuit 250 each cycle when the MOSFET turns off.

In another example, the off-line regulator 220 may include a source Scoupled to a first end of the primary coil 208 and the drain D coupledto a first end of the second capacitor 218. In this example, the firstend of the second capacitor 218 may be coupled to the drain D of theoff-line regulator 220 and the second end coupled to the second end ofthe primary coil 208.

In an example embodiment, the drain D of the off-line regulator 220 mayalso be coupled to the second end of the inductor 214. A control C ofthe off-line regulator 220 may be coupled to a first end of the thirdcapacitor 222. The source S of the off-line regulator 220 may also becoupled to a second end of the third capacitor 222 and to the first endof the primary coil 208.

In another example, the control circuit 210 may also include a firstresistor 224, a second resistor 226, a diode 228, and a fourth capacitor230. The diode 228 and fourth capacitor 230 may form a clamp networkmaintaining a voltage V_(OR) at the first end of the primary coil 208.The diode 228 may include a fast (t_(rr)<250 nanoseconds) or ultra-fastdiode to prevent the voltage across the off-line regulator 220 fromreversing and ringing below ground. The second resistor 226 may filterleakage inductance.

The first resistor 224 may, for example, have a resistance of about 59.3kiloohms. The fourth capacitor 230 may, for example, have a capacitanceof one microfarad and 100 volts.

In an example embodiment, the fourth capacitor 230 may include a firstend coupled to the source S of the off-line regulator 220 and to thefirst end of the primary coil 208. The fourth capacitor 230 may alsoinclude a second end coupled to a first end of the first resistor 224and to a cathode end of the diode 228. The first resistor 224 mayinclude a first end coupled to the second end of the fourth capacitor230 and to the cathode end of the diode 228. A second end of the firstresistor 224 may also include a second end coupled to the first end ofthe third capacitor 222 and to the control C. The diode 228 may includethe cathode end coupled to the first end of the first resistor 224 andto the second end of the fourth capacitor 230, and an anode end coupledto a first end of the second resistor 226. The second resistor 226 mayinclude the first end coupled to the anode end of the diode 228, and asecond end coupled to the second end of the second capacitor 218, thesecond end of the first capacitor 216, the bridge circuit 204, and thesecond end of the primary coil 208.

The off-line regulator 220 may, for example, include three operatingmodes. In a startup mode, an output voltage across the fourth capacitor230 may increase, and a current through the first resistor 224 and intothe control C may increase from approximately zero to two milliamperes.In a regulate mode, the off-line regulator 220 may maintain a constantvoltage across the third capacitor 222 by turning current into thecontrol C off when the voltage across the third capacitor 222 increases,and turn the current into the control C on when the voltage across thethird capacitor 222 decreases. In an auto-restart mode, which may betriggered by the voltage across the third capacitor falling so that thecurrent into the control C falls below approximately one milliampere,the off-line regulator 220 may return to the startup mode. The thirdcapacitor 222 may set the auto-restart period and the time for reachingthe regulate mode before entering the auto-restart mode from thestart-up mode.

The current inducing circuit 250 may include a secondary coil 252. Thesecondary coil 252 may carry a current induced by a changing magneticfield, such as the magnetic field induced by the primary coil 208. Thesolid line 240 indicates the magnetic coupling between the primary coil208 and the secondary coil 252. The secondary coil 252 may, for example,include a wire such as a copper wire wrapped around a pot core. Thesecondary coil 252 may surround an aperture (not shown in FIG. 2) whichreceives the probe which surrounds the primary coil 208, with, forexample, an air gap, such as an air gap of about 0.001 inches; theaperture is described further with reference to FIG. 6A.

The primary coil 208 and secondary coil 252 may form an isolationtransformer with the coils of the primary coil 208 and secondary coil252 wound around individual bobbins separated by the air gap. Thetransformer may be constructed in two sections corresponding to theprimary coil 208 and the secondary coil 252, each wound on separatebobbins using one half of the pot core and separated by the magnetic airgap of 0.001 inches. The transformer may be designed to bediscontinuous, so that energy may be transferred during the off time ofthe transistor 258.

The current inducing circuit 250 may include a delay switch 254 coupledto the secondary coil 252 and an output node 256 coupled to the delayswitch 254. The delay switch 254 may delay the current carried by thesecondary coil 252 from reaching the output node 256 to allow an outputvoltage of the output node 256 to reach a regulation voltage. The outputnode 256 may, for example, provide a voltage of approximately five voltsdirect current (DC) and 400 milliamperes.

The delay switch 254 may, for example, include a transistor 258, a firstcapacitor 260, and a first resistor 262. The transistor 258 may includea first end and a second end of a channel (such as a source and a drain)and a control node (such as a gate) which controls a resistance acrossthe channel. The first end may be coupled to a first end of thesecondary coil 252 and to a first end of the first capacitor 260. Thesecond end may be coupled to the output node 256. The control node maybe coupled to a second end of the first capacitor 260, all according toan example embodiment.

The first end of the first capacitor 260 may be coupled to the first endof the secondary coil 252 and to the first end of the channel of thetransistor 258. The second end of the first capacitor 260 may be coupledto the control node of the transistor 258. A first end of the firstresistor 262 may include a first end coupled to the second end of thefirst capacitor 260 and to the control node of the transistor 258, and asecond end coupled to ground 264, all according to an exampleembodiment.

In an example embodiment, the transistor 258 may include ametal-oxide-semiconductor field-effect transistor (MOSFET). Thetransistor 258 may, for example, include a p-channel MOSFET. The channelmay include a source-drain channel of the MOSFET, and the first end andsecond end may include a source and a drain, or vice versa. Also in thisexample, the control node may include a gate of the MOSFET.

The delay cause by the delay switch 254 may be a function of the RC timeconstant of the first capacitor 260 and the first resistor 262 and thesaturation threshold of the transistor 258. In an example in which thefirst capacitor 260 has a capacitance of approximately 0.15 microfaradsand the first resistor 262 has a resistance of approximately onemegaohm, the delay may be 150 milleseconds.

In an example embodiment, the current inducing circuit 250 may include asecond capacitor 266. The second capacitor 266 may rectify and filterthe output of the secondary coil 252 to provide a DC output at theoutput node 256.

The second capacitor 266 may have a capacitance of, for example, 22microfarads and 63 volts. A first end of the second capacitor 266 may becoupled to the first end of the secondary coil 252, the first end of thefirst capacitor 260, and to the first end of the channel of thetransistor 258. A second end of the second capacitor 266 may be coupledto the second end of the first resistor 262 and to ground 264, allaccording to an example embodiment.

Also in an example embodiment, the current inducing circuit 250 mayinclude a first diode 268 and a third capacitor 270. The first diode 268may, for example, include a Zener diode. The first diode 268 may preventa voltage of the output node 256 from exceeding a breakdown voltage ofthe first diode 268, such as approximately 5.6 volts. The thirdcapacitor 270 may reduce ripples in the voltage of the output node 256.

The third capacitor 270 may, for example, have a capacitance of 1000microfarads and 6.3 volts. The first diode 268 may include a cathode endcoupled to the second end of the channel of the transistor 258, to theoutput 256, and to a first end of the third capacitor 270. The firstdiode 268 may also include an anode end coupled to a second end of thethird capacitor 270, to the ground 264, to the second end of the firstresistor 262, and to the second end of the second capacitor 266. Thefirst end of the third capacitor 270 may be coupled to the second end ofthe channel of the transistor 258, to the first end of the first diode268, and to the output node 256. The second end of the third capacitor270 may be coupled to ground 264, to the second end of the first diode268, to the second end of the first resistor 262, and to the second endof the second capacitor 266, all according to an example embodiment.

In an example embodiment, the current inducing circuit 250 may include asecond diode 272, such as a Schottky diode. The second diode 272 mayrectify the output of the secondary coil 252 to provide a DC output atthe output 256. The second diode 272 may include a cathode end coupledto a second end of the secondary coil, and an anode end coupled to thesecond end of the second capacitor 266, to the second end of the firstresistor 262, to the anode end of the first diode 268, to the second endof the second capacitor 266, and to ground 264.

In an example embodiment, the current inducing circuit 250 may include asnubber circuit 274. The snubber circuit 274 may reduce transientvoltages between the second end of the secondary coil 252 and the ground264. The snubber circuit 274 may also attenuate conductedelectromagnetic interference, such as in high frequency bands.

The snubber circuit 274 may, for example, include a fourth capacitor 276and a second resistor 278 connected in series. The fourth capacitor 276may have a capacitance of 0.001 microfarads and 100 volts, according toan example embodiment. A first end of the snubber circuit 274 or seriesmay be coupled to the second end of the secondary coil 252 and to thecathode end of the second diode 272. A second end of the snubber circuit274 or series may be coupled to the anode end of the second diode 272,to the second end of the second capacitor 266, to the second end of thefirst resistor 262, to the anode end of the first diode 268, to thesecond end of the third capacitor 270, and to ground 264, all accordingto an example embodiment.

In an example embodiment, the current inducing circuit 250 may beincluded in a disk-shaped housing, such as the housing shown in FIG. 6A.The disk-shaped housing may enclose a disk with a plurality of magnetsmounted onto the disk, such as the disk shown in FIG. 6D. The disk mayrotate based on power received from the output node 256, according to anexample embodiment.

FIG. 3 is a circuit diagram showing a battery charging circuit 300according to an example embodiment. The battery charging circuit 300 mayinclude, for example, a voltage source 302 coupled to a motor input 304via a diode 306. The voltage source 302 may include, for example, theoutput node 256 shown in FIG. 2. The diode 306 may be coupled to themotor 104 (not shown in FIG. 3) and to the voltage source 302. The diode306 may allow current to flow from the voltage source 302 to the motor304. The motor input 304 may provide power to the motor 104. The motor104 may spin a disk (shown in FIG. 6D) upon which a plurality of magnetsare mounted, according to an example embodiment.

The battery charging circuit 300 may also include the rechargeablebattery 102. The rechargeable battery 102 may, for example, include alithium ion battery. The battery charging circuit 300 may recharge therechargeable battery 102 with the voltage source 302, and may enable therechargeable battery 102 to supply power to the motor 104, such as whena voltage of the voltage source 302 drops below a threshold voltagelevel, according to an example embodiment.

The battery charging circuit 300 may include a metal-oxide-semiconductorfield-effect transistor (MOSFET) 308. The MOSFET 308 may include a gatecoupled to the voltage source 302 and a source-drain channel coupled tothe rechargeable battery 102. For example, a source or a drain of theMOSFET 308 may be coupled to the rechargeable battery 102.

According to an example embodiment, the MOSFET 308 may include ap-channel MOSFET which allows current to flow from the rechargeablebattery 102 through the MOSFET 308 to the motor input 304 only when avoltage level of the voltage source 302 drops below a threshold voltagevalue. In this example, the MOSFET 308 may allow the voltage source 302,but not the rechargeable battery 102, to supply power to the motor 104via the motor input 304 when the voltage level of the voltage source 302exceeds the threshold voltage value. However, when the voltage level ofthe voltage source 302 drops below the threshold voltage value, therechargeable battery 102 may supply power to the motor 104 via the motorinput 304. The diode 306, which may include a Schottky diode, mayprevent current from flowing from the rechargeable battery 102 back tothe voltage source 302.

In an example embodiment, the battery recharging circuit 300 may includea battery charger 310. The battery charger 310 may include a supplyvoltage pin (VEE) coupled to the voltage source 302, and a battery pin(BAT) coupled to the rechargeable battery 102. The battery charger 310may, for example, include a single cell lithium-ion battery chargerusing a constant-current/constant voltage algorithm. The battery charger310 may deliver 400 milliamperes of charge current with a final floatvoltage accuracy of ±1%. The battery charger 310 may include an internalp-channel MOSFET and thermal regulation circuitry.

According to an example embodiment, the battery charging circuit 300 mayinclude a microprocessor 108 (not shown in FIG. 3). The microprocessor108 may control the motor 104, and may include a voltage monitor pin(pin 2) which receives a signal from the rechargeable battery 102. Thevoltage monitor pin may be coupled to the rechargeable battery 102 via afirst resistor 312, for example. The voltage monitor pin and firstresistor 312 may be grounded via a first capacitor 314 and secondresistor 316 connected in parallel, according to an example embodiment.

The first resistor 312 may, for example, have a resistance of about onemegaohm. The second resistor 316 may, for example, have a resistance ofabout 100 kiloohms. The first capacitor 314 may, for example, have acapacitance of about 0.1 microfarads.

The microprocessor 108 may also include at least one charging monitorpin which receives a signal from a charge pin (CHRG) of the batterycharger 310. The microprocessor 108 may, for example, include a pin 3which is directly coupled to the charge pin of the battery charger 108,and a pin 6 which is coupled to the charge pin of the battery charger108 via a third resistor 318. The third resistor 318 may, for example,have a resistance of about 2.49 kiloohms.

In an example embodiment, the battery charging circuit 300 may include avoltage regulator 320. The voltage regulator 320 may, for example,regulate the voltage of the rechargeable battery 102 and supply aregulated voltage VCC to the microprocessor 108. The regulated voltageVCC may, for example, be approximately 3.3 volts. The voltage regulator320 may, for example, include a TPS77033 low-dropout voltage regulatorwith low dropout voltage, ultra-low power operation, and miniaturizedpackaging. A bypass capacitor 326, which may have a capacitance of about0.1 microfarads, may improve transient response and noise rejection. Anoutput capacitor 328, which may have a capacitance of about tenmicrofarads, may stabilize the internal control loop of the voltageregulator 320.

In an example embodiment, the battery charging circuit 300 may begin acharge cycle when a voltage at the voltage source 302 rises above anunder voltage lock out (UVLO) threshold level with a fourth resistor 322(which may, for example, have a resistance of about 2.49 kiloohms)coupled between a programming pin (PROG) of the battery charger 310 andground, or when a battery is coupled to the charger output (CHRG) of thebattery charger 310. If at battery pin (BAT) of the battery charger 310falls below a threshold voltage level, such as approximately 2.9 volts,the battery charger may enter a trickle charge mode. In the tricklecharge mode, the battery charger 310 may emit a current, such asapproximately 40 milliamperes or 1/10 of a programmed charge current,from the charger output to bring the voltage of the rechargeable battery102 to a safe level for full current charging. If the battery pinvoltage rises above the threshold voltage level such as approximately2.9 volts, the battery charger 310 may enter a constant-current mode,and may emit a current, such as 400 milliamperes or the programmedcharge current, from the charger output to the rechargeable battery. Ifthe battery pin reaches a final float voltage, such as 4.2 volts, thebattery charger 310 may enter a constant-voltage mode and reduce thecurrent emitted from the charger output. The charge cycle may end whenthe current drops below a threshold value, such as 40 milliamperes or1/10 of the programmed value. At the end of the charge cycle, thebattery charger 310 may stop providing any current through the batterypin.

The charge current may be programmed for the programmed value, such as400 milliamperes, using the fourth resistor 322 between the programmingpin to ground. The fourth resistor 322 may, for example, have aresistance of 2.49 kiloohms to set the programmed charge current at 400milliamperes.

The battery charger 310 may detect the end of the charge cycle, such asby using an internal, filtered comparator to monitor the programmingpin. The battery charger 310 may terminate charging when a voltage valueof the programming pin falls below a threshold for a specified period oftime, such as below 100 millivolts for one millisecond. In response todetecting the end of the charge cycle, the battery charger 310 may entera standby mode and latch off the charge current. In the standby mode,the battery charger 310 may monitor the voltage level of the batterypin. If the voltage of the battery pin drops below a recharge threshold,such as approximately 4.05 volts, the battery charger 310 may beginanother charge cycle and supply current to the rechargeable battery 102.The battery charger 310 may also begin another recharge cycle inresponse to the magnetic field being removed and reapplied to thesecondary coil 252, such as when the charging probe (shown in FIG. 6B)is removed and reinserted.

In an example embodiment, the charger output of the battery charger 310may have three states: a strong pull-down state, a weak pull-down state,and a high impedance state. In the strong pull-down state, a relativelylarge current, such as approximately twenty milliamperes, may flow outof the charger output. The strong pull-down state may indicate that thebattery charger is in a charge cycle. Once the charge cycle has ended,the state of the charger output may be determined by undervoltagelockout conditions.

In the weak pull-down state, a relatively small current, such asapproximately two milliamperes, may flow out of the charger output. Theweak pull-down may indicate that the voltage source 302 meets the UVLOconditions and the battery charger 310 is ready to charge. The highimpedance state, with no current flowing out of the charging output, mayindicate that the battery charger 310 is in UVLO mode, because eitherthe voltage source 302 is less than a threshold voltage, such as 100millivolts, above the battery pin voltage, or insufficient voltage isapplied to the voltage source 302.

In an example embodiment, the microprocessor 108 (not shown in FIG. 3)may distinguish between the strong pull-down, weak pull-down, and highimpedance modes. The microprocessor 108 may, for example, detect thestrong pull-down state indicating that the battery charger 310 is in acharge cycle by forcing a digital output pin 6 into a high impedancestate and measuring a voltage at pin 3. An N-channel MOSFET (not shown),which may be included in the battery charger 310, may pull the chargepin low despite the voltage at the third resistor 318.

When the charge cycle has terminated and the charger output of thebattery charger 310 is in the weak pull-down state, emitting therelatively small current, such as approximately two milliamperes, thevoltage of the pin 3 may be pulled high by the third resistor 318. Themicroprocessor 108 may determine if there is a relatively small currentindicating the weak pull-down state by, for example, forcing the digitaloutput pin 6 into a low impedance state. The relatively high current maypull the pin 3 low through a fifth resistor 324, which may have aresistance of, for example, about one megaohm.

The microprocessor 108 may determine that the charger output is in thehigh impedance mode, indicating that the battery charger 310 is in UVLOmode, based on the pin 6 being pulled into a high impedance state andmeasuring the voltage on pin 3.

The microprocessor 108 may monitor the voltage of the rechargeablebattery 102, such as via pin 2. Monitoring the voltage of therechargeable battery 102 may allow the microprocessor 108 to determinethe energy capacity of the rechargeable battery 102. The first resistor312 and second resistor 316 may form a voltage divider network. Thevoltage divider network may scale the voltage to acceptable limits ofthe pin 2 of the microprocessor 108. The first capacitor 314 may act asa bypass capacitor. The microprocessor 108 may, for example, measure thevoltage at pin 2 and multiply by the ratio of the first resistor 312 tothe second resistor 316 to determine the voltage of the rechargeablebattery 102.

In an example embodiment, a housing (shown in FIG. 6A) may enclose thevoltage source 302, the diode 306, the rechargeable battery 102, and themotor 104. The housing may be disk-shaped, may include no electricalcontacts on an outside surface of the housing, and/or may be waterproof.

FIG. 4 is a circuit diagram showing the visual indicating circuit 400according to an example embodiment. The visual indicating circuit 400may include the microprocessor 108 and a plurality of visual indicators106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 i. Theplurality of visual indicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f,106 g, 106 h, 106 i may, for example, include a plurality oflight-emitting diodes (LESs). While nine visual indicators 106 a, 106 b,106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 i are shown in FIG. 4, thevisual indicating circuit 400 may include any number of visualindicators.

The microprocessor 108 may monitor the voltage level of the rechargeablebattery 102 (not shown in FIG. 4) and light a number of the plurality ofvisual indicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106h, 106 i. The number may, for example, be based on the monitored voltagelevel. For example, if the rechargeable battery 102 is fully charged,all of the plurality of visual indicators 106 a, 106 b, 106 c, 106 d,106 e, 106 f, 106 g, 106 h, 106 i may be turned on; if the rechargeablebattery 102 is less than fully charged, then a proportionate number ofthe plurality of visual indicators 106 a, 106 b, 106 c, 106 d, 106 e,106 f, 106 g, 106 h, 106 i may be turned on. The microprocessor 108 mayturn on the number of the plurality of visual indicators 106 a, 106 b,106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 i by turning the number ofthe plurality of visual indicators 106 a, 106 b, 106 c, 106 d, 106 e,106 f, 106 g, 106 h, 106 i on and off at a frequency that isimperceptible to a human eye, according to an example embodiment.

While not shown in FIG. 4, the visual indicating circuit 400 may alsoinclude the motor 104 which spins the disk upon which is mounted theplurality of magnets. As shown in FIG. 6D, the plurality of magnets maybe mounted onto the disk in a circular pattern with alternatingpolarities. The microprocessor 108 may, for example, cause the motor 104to spin the disk for a predetermined time duration. While the motor 104is spinning the disk, the microprocessor 108 may light all of theplurality of visual indicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f,106 g, 106 h, 106 i in a rotational sequence, according to an exampleembodiment. The microprocessor may light all of the plurality of visualindicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 iin the rotational sequence by, for example, periodically providing clockpulses to the counter 402. A frequency of the lighting the plurality ofvisual indicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106h, 106 i in the rotational sequence may increase during an end portionof the predetermined time duration. The increase in the frequency mayalert a user that the therapy cycle is almost over.

While also not shown in FIG. 4, the visual indicating circuit 400 mayalso include the rechargeable battery 102 which supplies power to themotor 104. The rechargeable battery 102 may also supply power to themicroprocessor 108, such as via the voltage regulator 320 (not shown inFIG. 4). According to an example embodiment, the microprocessor 108 maycause the motor 104 to spin the disk upon determining that an outsidepower source (such as the magnetic field induced by the charging probecircuit 200) has been removed from the visual indicating circuit 400and/or the rechargeable battery 202, and/or upon determining that thevoltage level of the rechargeable battery 102 exceeds a thresholdvoltage level.

The microprocessor 108 may, for example, light the plurality of visualindicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 ivia a counter 402. The counter 402 may, for example, include a CD74HC4017 decade counter clocked by the microprocessor 108. The counter 402may include a high-speed silicon gate complimentary metal-oxidesemiconductor (CMOS) five-stage Johnson counter with ten decodedoutputs. The outputs may normally remain low, and sequentiallytransition from low to high at the low to high transitions of the clockinput (CLK).

The microprocessor 108 may light the plurality of visual indicators 106a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 i via thecounter 402 by, for example, periodically providing a number of clockpulses and a reset pulse to the counter 402. For example, themicroprocessor 108 may sequentially provide a number of clock pulses tothe counter 402 equal to the number of the plurality of visualindicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 iwhich are to light or turn on, and then provide the reset pulse to thecounter 402. After providing the reset pulse to the counter 402, themicroprocessor 108 may provide the number of clock pulses to the counter402 and then the reset pulse, and so on. The microprocessor 108 mayprovide the clock pulses by providing inputs to a clock pin (CLK) of thecounter 402, and may provide the reset pulses by providing inputs to areset pin (RESET) of the counter 402, according to an exampleembodiment.

According to an example embodiment, the visual indicating circuit 400may include an audible output element 404. The audible output element404 may, for example, include a piezoelectric horn capable of producinghigh frequency beeps, and may be driven by the counter 402. Themicroprocessor 108 may, for example, cause the audible output element404 to periodically emit an audible output, such as a beep, when themotor 104 is spinning.

The visual indicating circuit 400 may be included in a housing (shown inFIG. 6A). The housing may enclose the motor 104, the disk, therechargeable battery 102, and the microprocessor 108. The plurality ofvisual indicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106h, 106 i may be mounted in the housing. The housing may be disk-shaped,include no electrical contacts on an outside surface of the housing,and/or may be waterproof.

FIG. 5 is a circuit diagram showing the tachometer circuit 500 accordingto an example embodiment. The tachometer circuit 500 may include, forexample, a power source or motor input 304 which supplies power to themotor 104. The power source may, for example, include the rechargeablebattery 102. The tachometer circuit 500 may also include the motor 104.The motor 104, which may include a direct current (DC) motor, maycontrol a disk 502 upon which a plurality of magnets 504 may be mounted.The magnets 504 may, for example, be mounted onto the disk 502 in acircular manner with alternating polarities.

The tachometer circuit 500 may also include the tachometer 110. Thetachometer 110 may, for example, include a Melexis US4881, which mayinclude a bipolar Hall-effect switch designed with mixed signal CMOStechnology. The tachometer 110 may integrate a voltage regulator, Hallsensor with a dynamic offset cancellation system, a Schmitt trigger, andan open-drain output driver. The power to operate the tachometer 110,which may have a voltage of 3.3 volts in an example embodiment, may beprovided by the microprocessor 108, which in turn may be powered by theregulated voltage VCC.

The tachometer 110 may monitor a magnetic field generated by theplurality of magnets 504 and provide a signal to the microprocessor 108based on the monitored magnetic field. The magnetic coupling of thetachometer 110 to the magnetic field generated by the magnets 504spinning around the motor 104 is shown by the dashed line in FIG. 5. Thetachometer 110 may, for example, monitor a frequency of magnetic fluxgenerated by the plurality of magnets 504 and provide the signal to themicroprocessor 108 based on the frequency of magnetic flux. The signalmay, for example, include a pulse for each change of magnetic flux, orpulses with a frequency proportional to the speed of rotation of thedisk 502.

A resistor 506, which may have a resistance of ten kiloohms in anexample embodiment, may cause the signal output by the tachometer 110 tohave a voltage value between zero and the regulated voltage VCC, and maybe about 3.3 volts in an example embodiment. A filter capacitor 508,which may have a capacitance of 0.001 microfarads in an exampleembodiment, may filter out noise and stabilize the detected magneticfrequency.

The magnetic frequency generated by the magnets 504 may be a function ofthe number of poles and the rotation speed of the disk 502. In anexample in which the disk 502 includes ten poles (ten magnets 504 withalternating polarities N-S-N-S-N-S-N-S-N-S), one complete rotation bythe disk 502 may generate five sinusoidal magnetic cycles. The motor 104may generate a prescribed frequency of, for example, 100 magnetic cyclesper second (CPS) by rotating the disk 502 twenty rotations per second(20 rotations per second×5 sinusoidal magnetic cycles per rotation=100cycles per second).

The tachometer circuit 500 may also include a microprocessor, which maybe the same microprocessor 108 included in the visual indicating circuit400. A capacitor 510, which may have a capacitance of 0.15 microfaradsin an example embodiment, may reduce high frequency noise on theregulated voltage VCC. The microprocessor 108 may control the motor 104based on the signal received from the tachometer 110. The microprocessor108 may, for example, control the motor 104 based on the signal bycomparing the signal to a reference signal. In an example embodiment,the microprocessor 108 may cause the motor 104 to increase or decreasethe speed of rotation of the disk 502 and magnets 504 to maintain adesired strength of the magnetic field.

The microprocessor 108 may control the motor 104 by controlling acurrent flowing through the motor 104. The motor 104 may, for example,include a precision DC motor with gold brushes. For example, if themicroprocessor 108 determines, based on the signal received from thetachometer 110, that the frequency of magnetic flux is too low, themicroprocessor 108 may increase the speed of rotation of the disk 502 byallowing current to flow through the motor 104. Or, if themicroprocessor 108 determines that the frequency of magnetic flux is toohigh, the microprocessor may decrease the speed of rotation of the disk502 by not allowing current to flow through the motor 104. Themicroprocessor 108 may control the motor 104 by applying an input to atransistor 506 which is connected in series with the motor 104. Theinput may, for example, take the form of pulse width modulation (PWM).Applying the input to the transistor 506 may vary a resistance of thetransistor 506 and thereby vary the power available to the motor 104 tospin the disk 502. The transistor 506 may, for example, include ametal-oxide-semiconductor field-effect transistor (MOSFET); in thisexample, the microprocessor 108 may control the motor 104 by controllinga voltage applied to a gate of the MOSFET. A diode 512 may allow anyreverse-biased voltage to dissipate without causing the motor 104 toreverse direction.

The tachometer circuit 500 may, for example, be included in a housing(shown in FIG. 6A). The housing may, for example, enclose the powersource or motor input 304, the motor 104, the disk 502, the tachometer110, and the microprocessor 108. The housing may be disk-shaped, have noelectrical contacts on an outside surface of the house, and/or may bewaterproof.

FIG. 6A is an illustration of a magnetic therapy device 600 according toan example embodiment. The magnetic therapy device 600 may, for example,include a housing 602. The housing 602 may be disk-shaped, such asapproximately the size of a hockey puck. The housing 602 may, forexample, have a five inch diameter and be two inches thick. The housing602 may include a Velcro strip (not shown), enabling a user to securethe magnetic therapy device to his or her body. The housing 602 may havenot electrical contacts on an outside surface of the housing 602,according to an example embodiment. The housing 602 may be waterproof.The housing may include an aperture 604.

The magnetic therapy device 600 may include the current inducing circuit250 (not shown in FIG. 6A). The current inducing circuit 250 may bemounted onto an inside surface (not shown) of the housing 602.

The current inducing circuit 250 may convert a magnetic field into adirect current (DC) voltage. In an example embodiment, the currentinducing circuit 250 may include the secondary coil 252. The secondarycoil 252 may induce a current from the magnetic field. The secondarycoil 252 may surround the aperture 604. The current inducing circuit 250may also include the delay switch 254 and the output node 256. The delayswitch 254 may be coupled to the secondary coil 252, and the output node256 may be coupled to the delay switch 254 and to the battery chargingcircuit 300.

The magnetic therapy device 600 may also include the battery chargingcircuit 300 (not shown in FIG. 6A). The battery charging circuit 300 maybe enclosed by the housing 602. The battery charging circuit 300 maycharge the rechargeable battery 102 based on the DC voltage. The batterycharging circuit 300 may also, based on the rechargeable battery 102,supply power to the motor 104 and to the microprocessor 108.

The magnetic therapy device 600 may also include the microprocessor 108(not shown in FIG. 6A). The microprocessor 108 may be enclosed by thehousing 102. The microprocessor 108 may control the plurality of visualindicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106i. The microprocessor 108 may also control the motor 104. Themicroprocessor 108 may, for example, be programmed so that each therapycycle of the magnetic therapy device 600, in which the motor 104 spinsthe disk 502 with the plurality of magnets 504, lasts approximatelytwenty minutes. The rechargeable battery 102 may, when fully charged,have enough energy to power twenty such therapy cycles, according to anexample embodiment.

The magnetic therapy device 600 may also include the plurality of visualindicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106i. The plurality of visual indicators 106 a, 106 b, 106 c, 106 d, 106 e,106 f, 106 g, 106 h, 106 i may be mounted onto the housing 602, and mayemit light outside the magnetic therapy device 600. While nine visualindicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106 h, 106 iare shown, the magnetic therapy device 600 may include any number ofvisual indicators 106 a, 106 b, 106 c, 106 d, 106 e, 106 f, 106 g, 106h, 106 i. The visual indicators 106 a, 106 b, 106 c, 106 d, 106 e, 106f, 106 g, 106 h, 106 i may indicate both the charge state of therechargeable battery 102 and the progress of a therapy cycle.

The magnetic therapy device 600 may also include the motor 104 (notshown in FIG. 6A). The motor 104 may generate a magnetic field byspinning the disk 502 upon which the plurality of magnets 504 aremounted.

FIG. 6B is an illustration of a charging probe 606 according to anexample embodiment. The charging probe 606 may include the chargingprobe circuit 200 (not shown in FIG. 6B). The primary coil 208 may, forexample, be included in a probe 608 which fits into the aperture 604 ofthe housing. The AC input 202 may, for example, be included in anelectrical power cord 610 which may plug into an electrical outlet toreceive AC power. The electrical power cord 610 may, for example,receive power from sources between about 85 and 275 volts AC and/or 47to 63 Hertz, allowing the charging probe 606 to charge the magnetictherapy device 600 from many electrical outlets.

FIG. 6C is an illustration of the magnetic therapy device 600 with thecharging probe 606 inserted according to an example embodiment. Thecharging probe 606 may, in the inserted position, supply power to themagnetic therapy device 600 with no electrical contacts.

FIG. 6D is an illustration of the disk 502 with the plurality of magnets504 according to an example embodiment. The magnets 504 may be mountedonto the disk 502 in a circular pattern with alternating polarities.

The magnetic therapy device 600 may, in an example embodiment, beself-contained, needing no outside components or inputs except thecharging probe 606. The magnetic therapy device 600 may be waterproofand/or water submersible, enabling a person to use the magnetic therapydevice 600 in a bathtub, for example. The magnetic therapy device mayalso be cleaned with soap and water, for example.

The magnetic therapy device 600 may also have no electrical contacts andrely completely on the rechargeable battery 102, which may bemagnetically coupled to the charging probe 606, for power. The transferof energy from the charging probe 606 to the magnetic therapy device 606by the magnetic field may make the magnetic therapy device safe fromelectrical shock hazards. The magnetic therapy device 600 may have noswitches, push buttons, or other such controls other than the chargingprobe 606.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. Elements of a computer may include atleast one processor for executing instructions and one or more memorydevices for storing instructions and data. Generally, a computer alsomay include, or be operatively coupled to receive data from or transferdata to, or both, one or more mass storage devices for storing data,e.g., magnetic, magneto-optical disks, or optical disks. Informationcarriers suitable for embodying computer program instructions and datainclude all forms of non-volatile memory, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor andthe memory may be supplemented by, or incorporated in special purposelogic circuitry.

Implementations may be implemented in a computing system that includes aback-end component, e.g., as a data server, or that includes amiddleware component, e.g., an application server, or that includes afront-end component, e.g., a client computer having a graphical userinterface or a Web browser through which a user can interact with animplementation, or any combination of such back-end, middleware, orfront-end components. Components may be interconnected by any form ormedium of digital data communication, e.g., a communication network.Examples of communication networks include a local area network (LAN)and a wide area network (WAN), e.g., the Internet.

While certain features of the described implementations have beenillustrated as described herein, many modifications, substitutions,changes and equivalents will now occur to those skilled in the art. Itis, therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the embodiments of the invention.

1. An apparatus comprising: a secondary coil configured to carry acurrent induced by a changing magnetic field; a delay switch coupled tothe secondary coil; and an output node coupled to the delay switch,wherein the delay switch comprises: a transistor including a first endand a second end of a channel and a control node configured to control aresistance across the channel, the first end being coupled to a firstend of the secondary coil and to a first end of a first capacitor, thecontrol node being coupled to a second end of the first capacitor, and asecond end of the channel being coupled to the output node of theapparatus; the first capacitor, the first capacitor including the firstend coupled to the first end of the secondary coil and to the first endof the channel, the first capacitor further including the second endcoupled to the control node; and a first resistor, the first resistorincluding a first end coupled to the second end of the first capacitorand to the control node of the transistor, the first resistor furtherincluding a second end coupled to ground.
 2. The apparatus of claim 1,wherein the secondary coil includes a wire wrapped around a pot core. 3.The apparatus of claim 1, wherein the secondary coil includes a copperwire wrapped around a pot core.
 4. The apparatus of claim 1, wherein:the transistor includes a metal-oxide-semiconductor field-effecttransistor (MOSFET); the channel includes a source-drain channel of theMOSFET; and the control node includes a gate of the MOSFET.
 5. Theapparatus of claim 1, further comprising a second capacitor, the secondcapacitor including a first end coupled to the first end of thesecondary coil, the first end of the first capacitor, and the first endof the channel, the second capacitor further including a second endcoupled to the second end of the first resistor and to the ground. 6.The apparatus of claim 5, further comprising: a first diode, the firstdiode including a cathode end coupled to the second end of the channel,to the output, and to a first end of a third capacitor, the first diodefurther including an anode end coupled to a second end of the thirdcapacitor, to the ground, to the second end of the first resistor, andto the second end of the second capacitor; and the third capacitor, thethird capacitor including the first end coupled to the second end of thechannel, the first end of the first diode, and the output, the thirdcapacitor further including a second end coupled to the ground, to thesecond end of the first diode, to the second end of the first resistor,and to the second end of the second capacitor.
 7. The apparatus of claim6, wherein the first diode includes a Zener diode.
 8. An comprising asecondary coil configured to carry a current induced by a changingmagnetic field; a delay switch coupled to the secondary coil; and anoutput node coupled to the delay switch, wherein the delay switchcomprises: a transistor including a first end and a second end of achannel and a control node configured to control a resistance across thechannel, the first end being coupled to a first end of the secondarycoil and to a first end of a first capacitor, the control node beingcoupled to a second end of the first capacitor, and a second end of thechannel being coupled to the output node of the apparatus; the firstcapacitor, the first capacitor including the first end coupled to thefirst end of the secondary coil and to the first end of the channel, thefirst capacitor further including the second end coupled to the controlnode; and a first resistor, the first resistor including a first endcoupled to the second end of the first capacitor and to the control nodeof the transistor, the first resistor further including a second endcoupled to ground; a second capacitor, the second capacitor including afirst end coupled to the first end of the secondary coil, the first endof the first capacitor, and the first end of the channel, the secondcapacitor further including a second end coupled to the second end ofthe first resistor and to the ground; a first diode, the first diodeincluding a cathode end coupled to the second end of the channel, to theoutput, and to a first end of a third capacitor, the first diode furtherincluding an anode end coupled to a second end of the third capacitor,to the ground, to the second end of the first resistor, and to thesecond end of the second capacitor; and the third capacitor, the thirdcapacitor including the first end coupled to the second end of thechannel, the first end of the first diode, and the output, the thirdcapacitor further including a second end coupled to the ground, to thesecond end of the first diode, to the second end of the first resistor,and to the second end of the second capacitor; and a second diodeincluding a cathode end coupled to a second end of the secondary coil,the second diode further including an anode end coupled to the secondend of the second capacitor, to the second end of the first resistor, tothe anode end of the first diode, and to the ground.
 9. The apparatus ofclaim 8, wherein the second diode includes a Schottky diode.
 10. Theapparatus of claim 8, further comprising a snubber circuit configured toreduce transient voltages between the second end of the secondary coiland the ground.
 11. The apparatus of claim 8, further comprising: afourth capacitor and a second resistor connected in series, the seriesincluding a first end coupled to the second end of the secondary coiland to the cathode end of the second diode and a second end coupled tothe anode end of the second diode, to the second end of the secondcapacitor, to the second end of the first resistor, to the anode end ofthe first diode, to the second end of the third capacitor, and to theground.
 12. The apparatus of claim 1, wherein the apparatus is includedin a disk-shaped housing, the disk-shaped housing enclosing a disk witha plurality of magnets mounted onto the disk with alternatingpolarities, the disk being configured to rotate based on power receivedfrom the output.
 13. The apparatus of claim 1, further including ahousing which encloses the secondary coil, the delay switch, and theoutput node.
 14. The apparatus of claim 13, wherein the housing isdisk-shaped.
 15. The apparatus of claim 13, wherein the housing includesno electrical contacts on an outside surface of the housing.
 16. Theapparatus of claim 13, wherein the housing is waterproof.
 17. Themagnetic therapy device of claim 13, wherein: the housing includes anaperture; and the secondary coil surrounds the aperture.
 18. Theapparatus of claim 1, further comprising: a battery charging circuitconfigured to charge a rechargeable battery based on power from theoutput node, and to supply power to a motor and to a microprocessorbased on the rechargeable battery; the microprocessor configured tocontrol a plurality of visual indicators and to control a motor; thevisual indicators configured to emit light outside the apparatus; themotor configured to generate a magnetic field by spinning a disk uponwhich is mounted a plurality of magnets; and a housing which enclosesthe battery charging circuit, the microprocessor, and the motor, and inwhich are mounted the secondary coil, the delay switch, the output nodeand the visual indicators.
 19. The apparatus of claim 18, wherein therechargeable battery is further configured to supply power to themicroprocessor via a voltage regulator.
 20. The apparatus of claim 18,wherein the microprocessor is configured to light the number of theplurality of visual indicators via a counter.
 21. The apparatus of claim18, wherein the microprocessor is further configured to light the numberof the plurality of visual counters by periodically providing a numberof clock pulses and a reset pulse to a counter.
 22. The apparatus ofclaim 18, further comprising: a tachometer, the tachometer beingconfigured to monitor a magnetic field generated by the plurality ofmagnets and provide a signal to the microprocessor based on themonitored magnetic field, wherein the microprocessor is configured tocontrol the motor based on the signal received from the tachometer. 23.The apparatus of claim 22, wherein the tachometer is configured tomonitor a frequency of magnetic flux generated by the plurality ofmagnets and provide the signal to the microprocessor based on thefrequency of magnetic flux.
 24. The apparatus of claim 1, furthercomprising: a second capacitor, the second capacitor including a firstend coupled to the first end of the secondary coil, the first end of thefirst capacitor, and the first end of the channel, the second capacitorfurther including a second end coupled to the second end of the firstresistor and to the ground; a first diode, the first diode including acathode end coupled to the second end of the channel, to the output, andto a first end of a third capacitor, the first diode further includingan anode end coupled to a second end of the third capacitor, to theground, to the second end of the first resistor, and to the second endof the second capacitor; and a second diode including a cathode endcoupled to a second end of the secondary coil, the second diode furtherincluding an anode end coupled to the second end of the secondcapacitor, to the second end of the first resistor, to the anode end ofthe first diode, and to the ground.